1. Field of the Invention
The present invention generally relates to a substrate processing apparatus, and more particularly to a substrate supporting apparatus making use of Bernoulli principle for supporting a substrate, such as a semiconductor wafer during cleaning, etching, developing, photo resist coating or removing process.
2. The Related Art
During a semiconductor device fabrication process, most treating processes used for manufacturing the semiconductor device, such as cleaning, etching, developing, photo resist coating or removing, focus on the substrate device side also referred to as the front side of the substrate. However, the substrate backside (non-device side) processing such as cleaning and etching is just as important. Contaminations attached on the backside of the substrate can cause for example photolithography steps defocus on the pattern formed on the front side of the substrate, and also can contaminate the substrate processing apparatus thereby contaminating other substrates processed by the same apparatus. Thereinto, backside metallic contaminations can diffuse through the substrate and contaminate the front side of the substrate, which would induce the semiconductor device electrical failure.
In order to ensure the quality of the semiconductor device, it is essential to clean the backside of the substrate. For cleaning the backside of the substrate, an apparatus is needed to support the substrate. Such apparatus has been known from U.S. Pat. No. 5,492,566. The apparatus comprises an annular nozzle in a circular surface of the apparatus. The nozzle is fed with compressed gas for the formation of a gas cushion between the apparatus and the substrate. The substrate is sucked above the apparatus by Bernoulli principle and keeps in a floating state. At least one projection in the apparatus topside surface serves as a rest for the substrate during processing. In the apparatus, the lower surface of the substrate facing the apparatus needs to keep contact with the projection. For the substrate backside processing, the substrate device side (front side) needs to face the apparatus topside surface. The projection may cause the device side pattern broken, and the gap height between the substrate and the apparatus topside surface is not to easily adjust.
Another apparatus for supporting a substrate is disclosed in U.S. Pat. No. 6,669,808. The apparatus provides a proximity suction member above a rotary base member having a support member supporting a substrate. The proximity suction member downwardly and outwardly injects gas from a support surface thereof to the overall peripheral edge of an upper surface of the substrate supported by the support member. The support surface being a lower surface of the proximity suction member is located on a plane substantially parallel to the substrate on the rotary base member. A processing solution supply part supplies the processing solution to a lower surface of the substrate supported and rotated on the rotary base member. Also the gap height between the lower surface of the substrate and the rotary base member topside surface is not easily to adjust. Besides the cleaning efficiency may be not so good because of the processing solution supply model.